Earnings Per share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Stock Option [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	2,494,428	2,417,613	2,494,428	2,417,613
Warrant [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	596,000	596,000	596,000	596,000
Restricted Stock Units (RSUs) [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	201,270	0	201,270	0